Peru's Belaunde strikes uneasy alliance with Army to contain rebels

With a leftist guerrilla insurgency stalking across parts of the Peruvian countryside, President Fernando Belaunde Terry lives with the fear that his three-year-old government could be its chief victim.

He has reason for concern. Although the guerrillas do not have much public support, they are a growing menace to the important Ayacucho region, just 200 miles from Peru's capital of Lima.

''Their next target could be Lima,'' says an adviser to President Belaunde, commenting on the spectacular coordination of a guerrilla strike on power lines near Lima last week that blacked out much of the capital for hours.

To cope with the guerrilla threat, President Belaunde reluctantly gave emergency power to the Peruvian military, headed by generals known to be unhappy with his presidency.

The President and his generals have long feuded. They overthrew him in a bloodless coup in 1968 when he was president. It was an era of economic crisis and Belaunde had lost much of his political support. Peruvians returned Belaunde to the presidency in 1980 as their first elected leader after the military stepped down.

Now the generals are again uncomfortable with Belaunde democratic idealism. And he is ill at ease with what he views as their heavy-handed tactics.

There is no assurance the military will honor its pledges to support him. President Belaunde is acutely aware of this. But as the guerrilla menace grew, he had little il14l,0,15l,4pchoice but to ask the military for help.

Operating easily among the rolling hills of the Ayacucho region, the guerrillas have become increasingly bold and violent - destroying power lines and blowing up government buildings. One of their tactics appears to be to terrorize peasants. It is estimated the leftists have killed at least 800 peasants in the past six months.

Many think the guerrillas' next targets could be closer to Lima - and even Lima itself. There is no mistaking the threat posed by the guerrillas.

''This is the most serious insurgency threat Peru has ever seen,'' the presidential adviser says.

A United States source adds: ''Belaunde had no choice. He had to call in the military. He had to impose martial law. He could not let the angry people in the guerrilla movement make any more headway.''

The guerrillas, many of whom are thought to be idealistic young men and women unhappy with Peru's perennial backwardness, call themselves the Sendero Luminoso (the Shining Light). Their ideology is leftist. They want something for Peru akin to Mao Tse-tung's revolt in China. They are not doctrinaire Marxists. Their propaganda often swipes at the Soviet Union and other Marxist societies as ''cruel deceptions.''

They particularly do not like Cuba under Fidel Castro - in marked contrast to earlier guerrilla movements in Peru.

So far, the military in stiff combat has cut deeply into guerrilla ranks - killing or capturing 600 guerrillas this year. But the Sendero still has an estimated 2,000 rebels under arms, and perhaps as many support personnel. To cope with this force, the Army has arrested hundreds in widespread dragnets throughout the country.